How to reorder arrange bars with in each Facet of ggplot

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One of the problems that we usually face with ggplot is that rearranging the bars in ascending or descending order. If that problem is solved using reorder() or fct_reorder(), the next problem is when we have facets and ordering bars within each facet.

Recently I came acrosss this function reorder_within() from the package tidytext (Thanks to Julia Silge and Tyler Rinker – who created this solution originally)

Example Code:


iris_gathered <- gather(iris, metric, value, -Species)

ggplot(iris_gathered, aes(reorder(Species, value), value)) +
  geom_bar(stat = 'identity') +
  facet_wrap(~ metric)

As you can see above, the bars in the last facet isn’t ordered properly. This is a problem you wouldn’t forget had you plotted TF_IDF or something similar with facets.

Here’s the solution

# reorder_within and scale_x_reordered work.
# (Note that you need to set scales = "free_x" in the facet)
ggplot(iris_gathered, aes(reorder_within(Species, value, metric), value)) +
   geom_bar(stat = 'identity') +
  #scale_x_reordered() +
  facet_wrap(~ metric, scales = "free_x")

Now, that’s beautifully done with a change in function.

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